This library intercepts seteuid and related calls, and simulates them
in a manner similar to the nss_wrapper and socket_wrapper
libraries. This allows us to enable the vfs_unixuid NTVFS module in
the build farm, which means we are more likely to catch errors in the
token manipulation.

The simulation is not complete, but it is enough for Samba4 for
now. The major areas of incompleteness are:

- no emulation of setreuid, setresuid or saved uids. These would be
needed for use in Samba3